What is the clinical evidence from this study?

Study design: Cross-Sectional. Population: Healthy adults (n=129). Intervention: Self-selected physical activity intensity based on guideline descriptors vs. Objective %HRmax ranges. Primary outcome: Self-selected moderate effort intensity (%HRmax).

May 16, 2014Open Access

Individuals Underestimate Moderate and Vigorous Intensity Physical Activity

Key Result

Adults correctly estimated light physical activity effort but significantly underestimated moderate (58.7% HRmax) and vigorous (69.9% HRmax) effort compared to established heart rate maximum ranges.

Study Design

Type

Cross-Sectional (n=129)

Blinding

Open-label

Randomization

Randomized order

Multicenter

Structured PICO

Population

129 adults (aged 18-64), 39 men and 90 women, recruited from York University, Canada.

Intervention

Self-selected walking/jogging pace on a treadmill corresponding to 'light', 'moderate', and 'vigorous' physical activity intensity descriptors from guidelines, performed in a randomized order for 2 to 3 minutes each.

Comparator

Objective percent heart rate maximum (%HRmax) ranges: 50-63% for light, 64-76% for moderate, and 77-93% for vigorous effort.

Outcome

Accuracy of self-selected physical activity intensity compared to objective %HRmax ranges.surrogate

Adults consistently underestimate the intensity of moderate and vigorous physical activity required for health benefits, suggesting current guideline descriptors may be inadequate.

Limitations

Large proportion of participants were younger (median age 20), requiring verification in older populations.
Unknown if participants could exercise at the self-selected pace for sufficiently long periods to obtain health benefits.
Unknown if descriptors would be used similarly on other exercise equipment such as a bike or elliptical.
Study initiated prior to the release of the revised 2011 CPAG, which may alter how descriptors are interpreted.
Unclear if underestimation is due to poor cardiovascular fitness or lack of exercise experience.

Abstract

BACKGROUND: It is unclear whether the common physical activity (PA) intensity descriptors used in PA guidelines worldwide align with the associated percent heart rate maximum method used for prescribing relative PA intensities consistently between sexes, ethnicities, age categories and across body mass index (BMI) classifications. OBJECTIVES: The objectives of this study were to determine whether individuals properly select light, moderate and vigorous intensity PA using the intensity descriptions in PA guidelines and determine if there are differences in estimation across sex, ethnicity, age and BMI classifications. METHODS: 129 adults were instructed to walk/jog at a "light," "moderate" and "vigorous effort" in a randomized order. The PA intensities were categorized as being below, at or above the following %HRmax ranges of: 50-63% for light, 64-76% for moderate and 77-93% for vigorous effort. RESULTS: On average, people correctly estimated light effort as 51.5±8.3%HRmax but underestimated moderate effort as 58.7±10.7%HRmax and vigorous effort as 69.9±11.9%HRmax. Participants walked at a light intensity (57.4±10.5%HRmax) when asked to walk at a pace that provided health benefits, wherein 52% of participants walked at a light effort pace, 19% walked at a moderate effort and 5% walked at a vigorous effort pace. These results did not differ by sex, ethnicity or BMI class. However, younger adults underestimated moderate and vigorous intensity more so than middle-aged adults (P<0.05). CONCLUSION: When the common PA guideline descriptors were aligned with the associated %HRmax ranges, the majority of participants underestimated the intensity of PA that is needed to obtain health benefits. Thus, new subjective descriptions for moderate and vigorous intensity may be warranted to aid individuals in correctly interpreting PA intensities.

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